Public resources are what I put on my blogs or web sites or what I mark to be public. As has been heavily discussed in this thread, Facebook has changed policies to make certain information public no matter what users choose in their privacy settings.

"how can you have a 'favorable reaction' to spam"

The intent is for people to lower their guard when they read email that's directly addressed to their name and seems to display knowledge of them.

"Abuse would make it reprehensible."

I think its abuse is being promoted, here. I mean, really, reread the blog post.